Girlfight visits another kind of woman warrior. Michelle Rodriguez scores a knockout debut as Diana Guzman, a trouble-prone Latina teen from the Brooklyn projects who decides, literally, to fight for her identity. Diana’s single father, Sandro (Paul Calderon), lays out hard cash at the gym so his son Tiny (Ray Santiago) can train to be a boxer. When Diana decides she’d be better in the ring than her timid brother, Sandro’s macho pride flares up. And that’s just for starters. Diana flaunts a fuck-you attitude that ticks off everyone she encounters, including Adrian (Santiago Douglas), the hottie boxer who finally wears down her defenses without ever convincing her that he can whup her ass.

Girlfight could have been Rocky on estrogen, or one of those Sundance favorites — it shared this year’s Grand Jury Prize — that allegedly make you feel warm all over, like the insufferably vapid Spitfire Grill. Instead, writer-director Karyn Kusama — a protege of indie king John Sayles — comes out punching. Kusama, an amateur boxer herself, shows none of the jitters of a first-time director; she’s spoiling to be heard. And what she’s done with the New Jersey-born Rodriguez, 22, an actress who’s never acted and a boxer who’s never boxed, is miraculous. It goes beyond the four months of boxing training that prepped the actress for the role. There are stunning close-ups of Rodriguez facing down the camera, flashing a dangerous glint that would scare off De Niro in Raging Bull. There’s tenderness, too, but minus the usual cutesy goo. Rodriguez’s love scenes with Douglas, another find, take on the quality of a sparring match in which each side only reluctantly gives quarter.usama uncovers layers in her characters that a lesser filmmaker would ignore in the rush to the final round. For example, Diana’s hostility toward her father is given as much weight as her bout with first love. Sandro used to slap Diana’s late mother into submission. It’s not a situation his daughter intends to replicate. Compared to Diana’s face-off with her father at home, the film’s big-finish bout with Adrian in the ring feels anticlimactic, not to mention contrived. But this is nitpicking. Girlfight is a strong, stinging film, alive with conflicts that defy glib resolutions. Rodriguez smolders with the beauty and intensity of a born star, and Kusama keeps her fearlessly on her feet with a movie that ducks no punches. Final decision: They’re both champions.